Sharpening quasar absorption lines with ESPRESSO

Vol. 651
4. Extragalactic astronomy

Sharpening quasar absorption lines with ESPRESSO

by P. Noterdaeme, S. Balashev, C. Ledoux, et al. 2021, A&A, 651, A78

Using EXPRESSO, with a resolution of around 2 km/s, the authors have revisited the high redshift quasi-stellar object HE 0001-2340, for which lower resolution observations were obtained with UVES. Those earlier data indicated anomalous Mg isotopic ratios for some of the intermediate redshift absorption systems. The new data yield essentially solar abundances. A striking result is the determination of the electron temperature for the high redshift component, about 1.6×104K, resolved into multiple velocity components within a range of a single galactic disk. The paper is a spectacular demonstration of the frontier opened by high resolution, high fidelity analysis of even single lines of sight, which can be used to tease out details of the evolution of galactic interstellar gas.